mp1517dr MPS, mp1517dr Datasheet - Page 5

• Manufacturer Part Number: mp1517dr
• Description: 3a, 25v, 1.1mhz Step-up Converter
• Manufacturer: MPS

OPERATION
The MP1517 uses a 1.1MHz fixed-frequency,
current-mode regulation architecture to regulate
the output. The operation of the MP1517 can be
understood by referring to the block diagram of
Figure 1. At the beginning of each cycle, the
N-Channel MOSFET switch is turned on,
forcing the inductor current to rise. The current
at the source of the switch is internally
measured and converted to a voltage by the
current
compared to the error voltage at COMP. The
voltage at the output of the error amplifier is an
amplified version of the difference between the
MP1517 Rev. 1.4
9/21/2007
OLS
EN
BP
SS
sense
15
3
4
7
16V
amplifier.
2.4V
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
0.9V
OSCILLATOR
SOFT-START
That
Figure 1—Functional Block Diagram
2.4V
+
+
--
--
voltage
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www.MonolithicPower.com
SGND
5, 13
is
MP1517 – 3A, 25V, 1.1MHz STEP-UP CONVERTER
IN
8
700mV reference voltage and the feedback
voltage. When these two voltages are equal,
the PWM comparator turns off the switch
forcing the inductor current to the output
capacitor through the external rectifier. This
causes the inductor current to decrease. The
peak inductor current is controlled by the
voltage at COMP, which in turn is controlled by
the output voltage. Thus the output voltage
controls the inductor current to satisfy the load.
The use of current-mode regulation improves
transient response and control loop stability.
CONTROL
LOGIC
PWM
CURRENT
SENSE
AMP
GM
+
--
--
+
0.7V
11, 12
9, 10
16
1
MP1517_BD01
FB
COMP
SW
PGND
5